In the mounting of duplex outlets, switches, and other electrical devices to the exterior of a building, two common practices are usually followed.
A first practice, usually followed on an unfinished exterior wall, involves mounting an electrical junction box within the wall. The electrical box is nailed or otherwise fastened to a wall stud with the junction box opening positioned to be roughly flush with the finished wall surface. An electrical box installed in this manner is usually termed a “recessed” box as it is recessed behind the outer wall of the building structure.
A second practice involves installing a “flush-mount” electrical box. This involves an electrical box that is nailed either directly to the outer surface of a building or to the substrate just below the outer surface. In either of these cases, as compared to the recessed electrical box, the flush-mount electrical box does not provide as much protection to the electrical box. In the flush-mount electrical box, at least a portion of the electrical box extends beyond the outer surface of the building, thereby making it prone to impact damage. A flush-mount electrical box mounted near the foundation, could, for example, be susceptible to damage caused by impacts from lawn mowers, vehicles, or other hazards.
Of the two common methods for installing electrical boxes on the exterior of buildings, the recessed box is by far the best method for providing an electrical box that is secure and less likely to be damaged by impacts. By recessing the electrical box in the wall, it is well protected against potential damaging impacts.
Although it is a simple practice to install exterior electrical boxes on an unfinished building in which wall studs are exposed, it is not quite as straightforward to install an electrical box on a finished wall. In this situation, usually termed a “retrofit”, an electrical box must be installed on a finished building. In this case, the mounting brackets on a typical electrical junction box are inadequate. The finished surface on the building, such as lapped siding, must be removed to expose the underlying substrate or sheathing to which the electrical box can be secured.
What is needed therefore is a recessed electrical box that is adaptable to being installed easily on a finished or an unfinished building.